Study of luminescence properties of dysprosium-doped CaAl12 O19 phosphor for white light-emitting diodes

Dy³⁺ -doped CaAl₁₂ O₁₉ phosphors were synthesized utilizing a combustion method. Crystal structure and morphological examinations were performed respectively using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques to identify the phase and morphology of the synthesized samples. Fourier transform infrared spectroscopy (FTIR) estimations were carried out using the KBr method. Photoluminescence properties (excitation and emission) were recorded at room temperature. CaAl₁₂ O₁₉ :Dy³⁺ phosphor showed two emission peaks respectively under a 350-nm excitation wavelength, centered at 477 nm and 573 nm. Dipole-dipole interaction via nonradiative energy shifting has been considered as the major cause of concentration quenching when Dy³⁺ concentration was more than 3 mol%. The CIE chromaticity coordinates positioned at (0.3185, 0.3580) for the CaAl₁₂ O₁₉ :0.03Dy³⁺ phosphor had a correlated color temperature (CCT) of 6057 K, which is situated in the cool white area. Existing results point out that the CaAl₁₂ O₁₉ :0.03Dy³⁺ phosphor could be a favorable candidate for use in white light-emitting diodes (WLEDs).

Structural and photoluminescence study of Mn2+-activated CaYAl3 O7 blue phosphors

The structural and photoluminescence properties of CaYAl3 O7 phosphor material doped with varying concentration of Mn(2+) have been studied. The phosphor material was synthesized by the combustion method at 500 °C and was characterized using X-ray diffraction, Fourier transform infrared spectroscopy and photoluminescence spectroscopy (PL). X-ray diffraction showed that the crystallites have average sizes in the range of ~58-70 nm. Corresponding Fourier transform infrared spectroscopy investigations confirm the phase formation and the presence of aluminate group (Al-O bands) in CaYAl3 O7 :Mn(2+) phosphor. Under the excitation at 356 nm wavelength, the PL spectra show the occurrence of two emission peaks obtained in the blue region at 389 nm and 412 nm, which is attributed to the 4 T1(G) → 6A1 transition of Mn(2+) ion. Upon increasing Mn(2+) concentration, the relative PL intensity shows an initial decrement followed by an increase displaying the effect of concentration quenching. Overall the results suggest the possibility of using this material in white lighting devices and plasma display panels.